1. Field of the Invention
The present invention relates to a micropattern transfer method and a micropattern transfer device for transferring a micropattern of a stamper to a transferred object.
2. Description of the Related Art
Conventionally, a photolithography technology is frequently used as the technology for processing a fine pattern needed in semiconductor devices, etc. Because, however, the pattern has been shrunk and a required process dimension has been shrunk as small as a light source wave length which is used for an exposure, it becomes difficult to process the fine pattern by the photolithography technology. For this reason, instead of the photolithography technology, an electron beam lithography apparatus which is a kind of a charged particle beam apparatus has been used. A pattern formation method of the electron beam lithography apparatus is different from a pattern formation method of a one-shot exposure method using a light source such as i-line and an excimer laser. That is, an exposure time (drawing time) increases as a number of patterns to be drawn increases. Therefore, a time required for the pattern formation increases in proportion to a degree of integration of a semiconductor integrated circuit, thereby resulting in significant reduction of a throughput.
In order to speed up the formation of patterns using the electron beam lithography apparatus, a technique of electron beam cell projection lithography has been developed, in which a plurality of combined masks having various shapes are irradiated with electron beams en bloc. However, such an electron beam lithography apparatus for use in the electron beam cell projection lithography is necessarily large-sized and high-priced, because a structure of the apparatus becomes more complex, and a mechanism for controlling each position of the masks with a higher accuracy is required.
In contradistinction to the above, a nanoimprint technology is well known as a technology for forming a fine pattern at low cost. In this nanoimprint technology, the fine pattern can be transferred by pressing a stamper having a concavity and convexity (surface configuration) corresponding to a concavity and convexity of the fine pattern (concavity and convexity pattern) to be formed onto, for example, a resin applied to a predetermined substrate. Also, this nanoimprint technology is considered to apply to formation of a memory bit in a mass storage medium, and pattern formation in a semiconductor integrated circuit. For example, substrates for the mass storage medium and the semiconductor integrated circuit can be manufactured by etching a thin film layer portion which is exposed at a concave portion of a pattern forming layer, and a substrate portion which contacts the thin film layer using a convex portion of the pattern forming layer formed by the nanoimprint technology as a mask.
An accuracy of etching at the substrate is affected by a distribution of thickness in a surface direction of a thin film layer. For example, assume a case where a thin film layer of a transferred object has a thickness difference of 50 nm between the maximum and the minimum. If the thin film layer is etched at a depth of 50 nm, a substrate is etched in a portion having a small thickness of the thin film layer. On the other hand, the substrate is not etched in a portion having a large thickness of the thin film layer. This means that, in order to ensure a prescribed accuracy of etching, the thickness of the pattern forming layer formed on a substrate needs to be uniform.
On the other hand, as methods for applying the resin in the nanoimprint technology, a spin coating method and an ink jet method can be considered. However, when the spin coating method is used for the nanoimprint technology, a large amount of resin is consumed, thereby resulting in increase in a process cost and an environmental load.
In contrast, the ink jet method requires a very small amount of resin because the resin in the form of fine droplets can be disposed discretely (in dot-pattern) on the substrate (e.g., see JP 2007-296738 A and JP 2008-178984 A). Therefore, when the ink jet method is used for the nanoimprint technology, the process cost and the environmental load can be decreased.
However, there is a problem that when the stamper is pressed onto the resin applied by the ink jet method, nonuniformity in thickness on the order of nm arises on the pattern forming layer between the substrate and the stamper.
Also, as described above, the pattern forming layer having such nonuniformity in thickness degrades the accuracy of etching.
Therefore, an object of the present invention is to provide a micropattern transfer method and a micropattern transfer device in which the small amount of resin is applied to a substrate, and the nonuniformity in thickness is prevented to arise on the obtained pattern forming layer.